Correspondence
Sildenafil and Ocular Perfusion
N Engl J Med 2000; 342:1680June 1, 2000
- Article
To the Editor:
Mild, transient visual changes such as increased sensitivity to light and color-tinge alterations occur in 3 percent of men who take sildenafil.1-3 We therefore assessed whether sildenafil could alter ocular perfusion.
We studied the right-eye responses in 12 normal adults (10 men and 2 women; mean [±SD] age, 36±3 years) before and after the oral administration of 50 mg of sildenafil (Viagra, Pfizer, New York). We measured intraocular pressure and pulsatile ocular blood flow by analyzing five consecutive tonometric ocular pulse waves (tonometer, OBF Laboratories, Malmesbury, United Kingdom), retinal microcirculation by Doppler velocimetry (HRF flowmeter, Heidelberg Engineering, Carlsbad, Calif.), brachial systolic and diastolic blood pressures, central retinal contrast sensitivity (7-degree pattern, 28 waves, 15 reversals per second), and visual fields (FDT visual field instrument, Humphrey Systems, Dublin, Calif.). The first four tests provide objective numerical data, and the last two psychophysical data. Measurements were obtained in random sequence in each of two sessions, once before and once 90 to 150 minutes after the administration of sildenafil. The study was approved by the local institutional review board, and all subjects gave informed consent for the study.
There were significant increases in pulsatile ocular blood flow (+29 percent, from 916±103 to 1185±158 μl per minute; P=0.02) and contrast sensitivity (+34 percent, from 92±11 to 122±11 log units; P=0.01) a mean of 110±8 minutes after the administration of sildenafil. Retinal microcirculation increased in seven of the nine eyes in which there were stable scans (+8 percent, P=0.09). The results of perimetry did not change significantly, nor did mean systolic and diastolic blood pressure, systemic pulse amplitude, or intraocular pressure. None of the subjects reported any subjective visual symptoms.
Pulsatile ocular blood flow occurs as a result of cardiac synchronous filling of the choroidal circulation, in which the majority of the ocular blood volume is found. The increase in pulsatile choroidal blood flow after the administration of sildenafil was probably due to dilatation of the choroidal vessels, because there were no changes in intraocular pressure or systemic pulse amplitude, which are other major determinants of choroidal blood flow.
In previous studies of normal subjects, contrast sensitivity decreased during hyperventilation-induced choroidal vasoconstriction.4 The apparent ability of sildenafil to increase contrast sensitivity while increasing pulsatile ocular blood flow should be further explored. Choroidal perfusion is diminished in patients with macular degeneration, a leading cause of acquired blindness5; therefore, drugs capable of increasing ocular perfusion might be of therapeutic value for various choroidal, retinal, and axonal disorders.
5 ReferencesWilliam E. Sponsel, M.D.
Gianmarco Paris, M.D.
Sal S. Sandoval, M.D.
Donald K. Sanford, M.D.
Joseph M. Harrison, Ph.D.
W. Rowe Elliott, B.S.
Yolanda Trigo, C.O.T.
University of Texas Health Science Center, San Antonio, TX 78284-62301
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